Computed tomography (CT)-guided biopsies have been performed since the early days of CT scanning when it became apparent that the cross sectional imaging modality offered unprecedented abilities to visualize the needle in cross section to verify positioning within a lesion. Over the last 15 years, the methodology for the CT-guided biopsy has remained largely one of trial and error. Essentially, a scan of the appropriate body part is made and a mental calculation of the trajectory is made following a depth calculation on the computer console. The depth is then transferred to the interventional device which has been marked. The interventional device is then inserted, removed, and reinserted repeatedly with repeat scanning at the appropriate interventional device position to confirm proper placement or improper placement. Obviously, this technique of trial and error introduces undesirable delays, risks, costs and, in some cases, exposure to unwanted radiation.
In addition to the matter of CT-guided biopsies, there has been much recent work in the field of MR-guided surgery, including biopsies and other minimally-invasive procedures. At present, methods of trajectory localization under MR are based largely on frameless stereotactic concepts. While this is a feasible methodology for many situations, there remains an issue of cost. To date, there has not been a method proposed that is simple, accurate, and inexpensive for use in the MR setting.
Therefore, there remains a need for a method for locating a interventional device in a body part which is faster and more convenient.